Simultaneous chemical species separation and T2* measurement using MRI

Abstract

A method for generating a magnetic resonance image is provided. A magnetic resonance imaging excitation is applied for a plurality of cycles at a cycle rate. A plurality of magnetic resonance image echoes is acquired for each cycle. A decay map is estimated from the plurality of magnetic resonance image echoes for each cycle. The estimated decay map is used to generate an image for at least two different species.

1. A method for generating a magnetic resonance image, comprising:
 a) applying a magnetic resonance imaging excitation for a plurality of cycles at a cycle rate; 
 b) acquiring a plurality of magnetic resonance image echoes for each cycle; 
 c) estimating a decay map from the plurality of magnetic resonance image echoes for each cycle; and 
 d) using the estimated decay map to generate an image for at least two different species. 
 
   
   
     2. The method, as recited in  claim 1 , wherein there exists at least two of the plurality of magnetic resonance image echoes for each cycle that their species phase angle difference is not k*π, where k is an integer. 
   
   
     3. The method as recited in  claim 2 , wherein the using the estimated decay map to generate an image for at least two different species applies a least squares process with the estimated decay map to determine species intensity. 
   
   
     4. The method as recited in  claim 3 , wherein the applied least squares process is an applied weighted least squares process. 
   
   
     5. The method, as recited in  claim 4 , wherein the weighted least squares process provides a lower weight to more decayed signals. 
   
   
     6. The method, as recited in  claim 5 , wherein the at least two different species are water and fat. 
   
   
     7. The method, as recited in  claim 6 , further comprising using the estimated decay map to generate an oxygen level map. 
   
   
     8. The method, as recited in  claim 7 , further comprising using the estimated decay map to generate an iron level map. 
   
   
     9. The method, as recited in  claim 8 , wherein the iron level map is used to generate the image for at least two species. 
   
   
     10. The method of  claim 9 , wherein the estimating a decay map from the plurality of magnetic resonance image echoes for each cycle uses at least two echoes per cycle. 
   
   
     11. The method of  claim 9 , wherein the estimating a decay map from the plurality of magnetic resonance image echoes for each cycle uses at least three echoes per cycle. 
   
   
     12. The method of  claim 9 , wherein the estimating a decay map from the plurality of magnetic resonance image echoes for each cycle uses at least six echoes per cycle. 
   
   
     13. The method, as recited in  claim 1 , wherein the at least two different species are water and fat. 
   
   
     14. The method, as recited in  claim 1 , further comprising using the estimated decay map to generate an oxygen level map. 
   
   
     15. The method, as recited in  claim 1 , further comprising using the estimated decay map to generate an iron level map. 
   
   
     16. The method, as recited in  claim 1 , further comprising estimating a field map from the plurality of magnetic resonance image echoes for each cycle. 
   
   
     17. The method of  claim 1 , wherein the estimating a decay map from the plurality of magnetic resonance image echoes for each cycle uses at least six echoes per cycle. 
   
   
     18. An apparatus for providing magnetic resonance images, comprising:
 a magnet system; 
 a controller electrically connected to the magnet system, comprising:
 a display; 
 at least one processor; and 
 computer readable media, comprising:
 computer readable code for applying a cyclical magnetic resonance imaging excitation for a plurality of cycles at a cycle rate; 
 computer readable code for acquiring a plurality of magnetic resonance image echoes for each cycle; 
 computer readable code for estimating a decay map from the plurality of magnetic resonance image echoes for each cycle; 
 computer readable code for using the estimated decay map to generate an image for at least two different species; and 
 computer readable code for displaying the generated image on the display. 
 
 
 
   
   
     19. The apparatus as recited in  claim 18 , wherein the using the estimated decay map to generate an image for at least two different species applies a least squares process with estimated decay to determine species intensity. 
   
   
     20. The apparatus as recited in  claim 18 , wherein the computer readable media further comprises computer readable code for estimating a decay map from the plurality of magnetic resonance image echoes for each cycle.